[00:00.70]Narrator: Listen to part of a lecture in a biology class.[00:05.30]FEMALE PROFESSOR: Ok. [00:06.88] There are two major types of classifiers in the world: people we call “lumpers” and people we call “splitters.” [00:14.33] A lumper is someone who tries to put as many things as possible in one category. [00:19.70] Splitters like to look for the differences and put things in as many different categories as possible.
[00:25.70]Both lumpers and splitters work in the business of defining biological classifications.[00:31.31]The Greek philosopher Aristotle is generally considered the first person to systematically categorize things. [00:37.95]He divided all living things into two groups—[00:40.91]they were either animal or vegetable. [00:43.25]And these categories are what biologists came to call kingdoms. [00:47.33] So if it ran around it was an animal... a member of the animal kingdom, [00:52.39]and if it stood still and grew in the soil it was a plant... a member of the plant kingdom. [00:58.66] This system–organizing all life into these two kingdoms– worked very well for quite a while, even into the age of the microscope.[01:06.74]With the invention of the microscope in the late 1500s, we discovered the first microorganisms; [01:13.70]we saw that some wiggled and moved around and others were green and just sat there. [01:19.46]So the ones that moved like animals were classified as animals, and the more plant-like ones as plants. [01:25.94]Oh, before I go on, I must mention Carolus Linnaeus…kah-ROE-lus Li-NAY-us.[01:29.64] A hundred years or so after the invention of the microscope, Carolus Linnaeus devised a simple and practical system for classifying living things, according to the ranks of categorization still in use today— class, order, family, and so on.
[01:44.66]And by far the best aspect of Linnaeus’ system is the general use of binomial nomenclature — having just two names to describe any living organism. [01:54.50]This replaced the use of long descriptive names, as well as common names which vary from place to place and language to language. [02:02.09] Binomial nomenclature gives every species a unique and stable two-word name, agreed upon by biologists worldwide.[02:11.44]But not everything about this system remained unchanged. [02:15.67] Take, for example, the mushroom... a fungus. [02:18.70] It grew up from the ground and looked like a plant. [02:22.20] So it was classified as a plant. [02:24.46] But using the microscope, we discovered that a fungus contains these microscopic thread-like cells that run all over the place.[02:32.80] and so it’s actually not that plant-like. [02:35.74] So in this case, the splitters eventually won, and got a third kingdom just for the fungus.[02:42.00]And as microscopes improved, we discovered some micro-organisms that were incredibly small. [02:48.55] I’m talking about bacteria. [02:50.50] And we could see that they didn’t have what we’d call a nucleus, [02:54.05] so they got their own kingdom— a kingdom of very tiny things without nuclei. [02:59.50] So then we had separate kingdoms for plants, and for animals. And the different kinds of fungus, like mushrooms. And for these tiny bacteria. [03:07.90] But we also had some other micro-organisms that didn’t fit anywhere. [03:12.41]So biologists gave them their own kingdom, [03:12.41] and this fifth kingdom was sort of an anything-that-doesn’t-fit-in-the-first-four kingdom, which upset some people.[03:21.91]And then there was the question of viruses. [03:25.03]Viruses have some characteristics of life, but don't reproduce on their own or use energy. [03:31.27] So we still don’t know what to do with them. [03:34.20] The lumpers want to keep viruses in the current system. [03:37.37] Some of the splitters say to give them a separate kingdom; [03:40.54]and the extreme splitters say that viruses have nothing at all to do with living things and “keep them out of my department.”[03:48.48]Recent research, though, has moved us in yet another direction. [03:52.63] Nowadays when we want to determine the characteristics of something, we look at its biochemistry and its genetic material. [04:00.22]And what we've discovered is that some bacteria are not like the others. [04:04.92] Many of these are called “extremophiles” EXTREME uh files. [04:07.77]They live in very strange places— in polar ice, or in the boiling water of hot springs; or in water so salty other organisms couldn't live there. [04:18.10] Extremophiles tend to have a different chemistry from other bacteria, a chemistry that, in some cases, is actually more related to plants and animals than to previously known bacteria.[04:28.78]So, what to do with these strange bacteria?
[04:33.19]Well, one thing we've done is create a new set of categories—the domains—overarching the different kingdoms. [04:40.44] Biologists now recognize three domains. [04:43.66] But even as we talk about these new domains, well…come back in a few years and it might all be different.
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